BONE-GROWTH AND REMODELING AFTER FRACTURE

We used a rabbit model to investigate the mechanism by which the angul ation of fractures is corrected in children. We produced a transverse proximal tibial fracture in one leg of 12 eight-week-old New Zealand w hite rabbits and measured bone alignment and length and the patterns o f bone growth and remodelling, The angle between the joint surfaces ch anged rapidly to correct the alignment of the limb as a result of asym metrical growth of epiphyseal plates, In an adult with closed plates, the angle between the joint surfaces cannot therefore improve, The ang le at the fracture itself showed slow improvement because of bone drif t and the asymmetrical growth of the epiphyseal plates, Remodelling co rrected the shape of the bone in the region of the fracture. Periostea l division on the convex side increased the growth of the epiphyseal p late on that side, thus slowing the correction, The effect was relativ ely small, providing an indication that factors other than the periost eum are important in inducing correction, External torsional deformiti es developed because of helical growth at the plate. This was probably caused by abnormal posture which induced a torque at the growth plate . Helical growth is the mechanism by which rotational deformities can occur and correct.